Suspended ceiling air distribution arrangement

ABSTRACT

A linear air plenum formed of duct board (generally a thickness of fiber glass) is connected to an elongated support pan. An elongated opening is provided in the pan and an arrangement of walls depends from the underside of the pan at the opening to form a collar registering with an air bar which includes diffuser elements and defines a slot in a suspended ceiling. Alternatively, a diffuser assembly is attached to the pan at the elongated opening in which case the slot is defined by an air track and the pan carried diffuser registers with the air track. In transverse cross section the air plenum is in the form of a polygon. The duct board is one-piece and relieved at the fold lines to facilitate folding to form the air plenum. The pan engages the air plenum, when so folded, to hold the duct board folded. The pan-air plenum combination is used in a ceiling having a series of main and cross runner T-bars; a number of such pan-air plenum combinations are connected end-to-end and arranged parallel to one of the series of cross runners or main runners and at right angles to and extending across the other. The length of the pan-air plenum combinations and the attached collar, or diffuser, are related to the module upon which the ceiling is constructed. Pivotal extractor blades are pivotally supported in the pan opening to direct air from the plenum through the air track or air bar. The pans are spaced above the main runners thereby providing alternating air supply and return areas.

United States Patent [191 Lambert 1 Nov. 11, 1975 1 SUSPENDED CEILINGAIR DISTRIBUTION ARRANGEMENT [75] Inventor:

[52] US. Cl 98/40 D; 98/40 C; 98/114 [51] Int. Cl. F24F 7/00 [58] Fieldof Search 98/40 R, 40 D, 40 DL, 40 C,

[56] References Cited UNITED STATES PATENTS 3,319,558 5/1967 Bodian98/40 D 3,352,076 11/1967 Jones v 98/40 D 3,353,472 11/1967 Lee et a198/40 D 3,383,999 5/1968 Fragnito et a1. 98/40 D 3,411,425 11/1968Lambert 98/41 R 3,420,439 l/l969 Meckler 98/40 DL 3,601,033 8/1971Lambert 3,690,243 9/1972 Lambert 3.757.667 9/1973 Lambert 98/40 DPrimary E.\'aminerWilliam E. Wayner Assistant E.rmninerl-lenry C. Yuen[57] ABSTRACT A linear air plenum formed of duct board (generally athickness of fiber glass) is connected to an elongated support pan. Anelongated opening is provided in the pan and an arrangement of wallsdepends from the underside of the pan at the opening to form a collarregistering with an air bar which includes diffuser elements and definesa slot in a suspended ceiling. Alternatively, a diffuser assembly isattached to the pan at the elongated opening in which case the slot isdefined by an air track and the pan carried diffuser registers with theair track. In transverse cross section the air plenum is in the form ofa polygon. The duct board is one-piece and relieved at the fold lines tofacilitate folding to form the air plenum. The pan engages the airplenum, when so folded, to hold the duct board folded. The pan-airplenum combination is used in a ceiling having a series of main andcross runner T- bars; a number of such pan-air plenum combinations areconnected end-to-end and arranged parallel to one of the series of crossrunners or main runners and at right angles to and extending across theother. The length of the pan-air plenum combinations and the attachedcollar, or diffuser, are related to the module upon which the ceiling isconstructed. Pivotal extractor blades are pivotally supported in the panopening to direct air from the plenum through the air track or air bar.The pans are spaced above the main runners thereby providing alternatingair supply and return areas.

15 Claims, 6 Drawing Figures U.S. Patent Nov. 11, 1975 Sheet 1 0143,918,354

U.S. Patent Nov. 11,1975 Sheet 3 of4 3,918,354

SUSPENDED CEILING AIR DISTRIBUTION ARRANGEMENT BACKGROUND OF INVENTIONIn discussing this invention reference has been, and

will be, made to a slot, an air bar, and an air t rack.'A' slot is anelongated, linear opening generally 1 inch to 2 inches wide, in asuspended ceiling defined between,

for example, the extremities of spaced ceiling support I members such asinverted T-bars. An air bar is a linear air diffuser, incorporating ameans of pattern control and including as part of its assembly thesupport mem{ bers (inverted T-bars) forming the slot. An air track isthe same as the air bar but does not include the pattern control, aseparate diffuser being used in association with the air track toprovide pattern control. Various air plenum constructions, diffuserconstructions, and combinations thereof have been provided in the past.Examples of such constructions can be found in various US. patentsissued to Robert R. Lambert, namely US. Pat. Nos. 3,227,063, 3,577,904,3,601,032, 3,601,033, 3,690,243, 3,748,998; and

This invention is concerned with such constructions and the problemspresented thereby.

SUMMARY OF rNvE TroN Some of the general objects of this invention areto provide an air delivery arrangement which is simple to assemble onsite, provides versatility :in available air supply and returncombinations, and which provides for efficient and economical shippingof the-basic elements of the air delivery arrangement.

For the achievement of these and "other objects-this invention proposesa combination including a generally elongated, linear basic pan to whichan airplenum is connected. An elongated opening is provided in the panand has a length which is less than the overall length of the panthereby providing a pan which is closed except for that opening. The panis spaced from the ceiling support members and the arrangement of theopening and the closed pan areas cooperate in providing supply andreturn areas the ceiling.

The pan-air plenum combination is used in a suspended ceiling. A slot isdefined in the-ceiling and the pan opening is arranged in alignmentwith' the slot,with means being provided at the pan opening for registrywith the slot so that air passing through the opening discharges throughthe slot. Preferably, the length of the pan opening is lessthan that ofthe slot so that the portion of the slot adjacent that registering withthe pan opening communicates with a closed portion ofthe pan and can beused to provide an air return.

Preferably, the plenum is in the shape ofa polygon in transverse crosssection. The plenum is formed from a one-piece duct member relieved atthe fold linesto facilitate folding at the job site while permitting theduct member to be shipped flat. The pan is provided with means forengaging the duct board. after it is folded to hold the duct board onthe pan in itsfolded shape. The duct board formed plenum is open at thepan opening so that air delivered into the plenum passes through theopening.

Preferably, a plurality of pans so constructed and with attached airplenums are arranged end-to-end along a ceiling slot to provide anelongated continuous air plenum. The ceiling includes a pattern ofceiling support members and the length of the pan. its opening, and thelength of the air plenum are related to the module on which the ceilingis constructed.

The means connected at the pan opening, or opening's, can be in the formof a collar engaging an air bar which defines the slot. Alternativelythe means can be a diffuser assembly, including its own pattern control,and engages an air track which defines the slot.

Other objects and advantages will be pointed out in, or be apparentfrom, the specification and claims, as will obvious modifications of theembodiments shown in the drawings, in which:

FIG/1 is a perspective view partially exploded of an air plenum-pancombination;

FIG. 2 is a side elevation of the arrangement of FIG. 1;

FIG. 3 is a section view taken generally along lines 3-3 of FIG. 2;

FIG. 4 is a section view taken generally along lines 44 of FIG. 2;

FIG. 5 isa partial section view of an alternative embodiment of theinvention;

FIG. 6 is a perspective view of a duct board section before it is foldedinto the air plenum shape; and

FIG. 7 is a perspective view partially exploded of yet anotheralternative embodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS With particular reference to FIG. 1of the drawings, anair delivery assembly 10 is illustrated as includingthree'airplenu'm duct sections 12, 14, and 16 made up of conventionalfoil covered duct board (generally a thickness of fiber glass). The airplenum duct sections are joined by tape strips 11 to define a continuousplenuni chamber 17 and are connected to support pans 18, 20, and 22. Theconstruction of the support pans and their connection to the plenumsections will be described more completely hereinafter. The ends of theplenum formed by plenum duct sections 12, I4, and 16, and partially bypans 18, 20, and 22, are closed by end plates 24 and 26 which again areconnected to their respective plenum sections 12 and 16 by tape strips11 and may be further fastened to the duct board by machine screws 13extending through horizontal portion 15 0f the ends and into pans 18 and22. Sheet metal collar 28 is suitably attached to plenum section 14 atopening 30 and will accept a flexible duct so that air from a centralair supply can be admitted into the plebar define a slot in the ceiling.Weir members 38 and 40 in the form of nested channel shaped membersextend the length of the air bar and are positioned between U-shapedretainers 42 and 44, a pair of such retainers being provided at theopposite ends of the air bar but only one pair being illustrated in FIG.3. The \veir members are held in the air bar but are free to movehorizontally relative to each other and T-bars 32 and provides pattern.and to some degree volume, control of air discharging from the air bar.The ends of the air bar are closed by end plates 39 only one of whichare illustrated in the drawings, i.e. FIG. 3. The construction,connection, and function of weirs 38 and 40 are more completelydescribed in Robert R. Lamberts US. Pat. Nos. 3,41 1,425 and 3,444,801and should additional description be necessary, reliance is herebyplaced on those patents. It is believed, however, that the abovedescription is sufficient for purposes of understanding this invention.

The air bar assembly just described provides an air diffuser andincorporates its own pattern control arrangements, i.e. the nestedweirs.

In accordance with conventional practice, slot 100 is generallycontinuous along the length of the ceiling, i.e. parallel to the mainrunners and can be either 1 inch or 2 inches or whatever width isdesired although 1 inch and 2 inch slots are most standard.

FIG. 5 illustrates an alternative arrangement for providing the slot inthe suspended ceiling. In this arrangement, main runners are againprovided and a pair of inverted T-bars 46, parallel to and having thesame construction as the main runners, are positioned adjacent eachother but spaced such that their horizontal flanges 48 define the slot102 which can have the same dimension as slot 100 as desired. Thisarrangement, i.e. the inverted T-bars 46 which do not include their ownpattern control arrangement is an air track.

In both of the just described arrangements, i.e. the air bar or airtrack, the conventional ceiling tile 36 is supported between thestandard main runners and the inverted T-bars 32 which make up eitherthe air track or air bar.

Returning now to FIG. 3 wherein the slot is defined by the air barassembly, the construction of the pan to cooperate with the air bar inproviding air supply, will be described. The description of one pan willsuffice for pans 18 and 22 which are identical in construction to pan20. Pan 20 includes a planar surface 21 terminating in longitudinalsides 58 and 60 which are turned up to provide upwardly extendingflanges, and also includes ends 23 and 25 (see FIG. 1). Spaced inwardlyof these sides 58 and 60 but parallel thereto, are a second pair ofupstanding flanges 50 and 54 which terminate in angled lip 52 and 56respectively. As illustrated, flanges 50 and 54 are cut from the basicpan and formed upwardly to leave an opening 62 therebetween. Except foropening 62, pan surface 21 is otherwise closed. A plurality of extractorblades are positioned in the opening 62. The plenum chamber 17 has opencommunication with opening 62, i.e. air flowing into the plenum chambercommunicates directly with opening 62 for passage through that openinginto the air bar or air track depending on the embodiment. The purposeof these extractors is to insure proper direction of the air deliveredto the air plenum chamber into the air bar or diffuser 39. Morespecifically, air under pressure delivered into the air plenum chamber17 will have a tendency to continue along a path parallel to thelongitudinal axis of the air plenum, the extractors turn the air flowgenerally vertically for passage (in FIG. 3) through the air bar andslot 100.

Structurally, a plurality of extractor blades 64, five as illustrated inFIG. 1, are supported between walls 68 and 70 spot welded to flanges 50and 54. Each of the extractors includes a pair of tabs 65 at theopposite sides thereof. These tabs are connected to walls 68 and 70 bypins 72 which form horizontal axis about which the extractors can bepivoted to vary the vertical orientation of extractor blades relative toair flow in the plenum. The extractors being pivotahle can vary thedirection of air, i.e. vertical, all at the same angle to thehorizontal, and at angles to the horizontal which are relativelydivergent. This adjustability as to the angle at which air can bedirected into the slot also results in adjustability of throw and spreadof air in the room being serviced and all at a substantially constantvolume of supply (cfm).

Shoulders 74 and 76 are provided in walls 68 and 70 and are adapted torest atop T-bars 32 thereby registering the air plenum opening 62 withthe air bar. Springs 78 and 80 connected to walls 68 and 70 hold the airplenum-pan combination assembled onto the air bar.

In the embodiment of FIG. 5, where the slot 102 is provided by an airtrack which does not include its own pattern control arrangement, adiffuser separate from the air track must be provided. In thisembodiment, the pivotal extractors 64 are supported between the upperportions 77 and 79 of side walls 82 and 84 of diffuser assembly 81. Forin this embodiment, in contrast to that of FIG. 3, a collar does notextend from the underside of the pan but instead a diffuser assembly 81and it defines the outlet opening 62'. Side walls 82 and 84 of thediffuser have horizontal extensions 83 each of which is spot welded tothe underside of pan 20. Side walls 82 and 84 extend downwardly forengagement with horizontal flanges 48 of inverted T-bars 46 and nestedweirs 138 and 140 are supported between walls 82 and 84 in the samemanner as described in connection with FIG. 3. That is, retainerchannels similar to 42 and 44 are provided at the opposite ends of thediffuser. Again, the opposite ends of the diffuser are closed by endplates 85 only one of which is illustrated in FIG. 5.

With reference to FIG. 2, it can be seen that the air bar assembly 39,and also the diffuser assembly 81, are of limited length relative to thelength of pans 18, 20, and 22 and air plenums 12, 14, and 16. Asillustrated, the lengths of the air bar assemblies, and the air trackassemblies is generally equal to the distance between adjacent crossT-bars 41 thus providing spaced air supply areas above slot 100, or 102.

With this arrangement, it is relatively simple to provide for airreturn, since openings 62 are the only openings in the pans and the pansare otherwise closed. Namely, those areas of the pans overlying thoseportions of the slot adjacent to or between adjacent air bar or airtrack, assemblies are closed can be used to provide for return air intothe attic between the suspended ceiling and the actual structuralceiling. The return air arrangement is illustrated in FIG. 4 and FIG. 2.As can be seen in the drawings, the pans are spaced from the upper endsof the main runners, and the cross runners. This leaves a space betweenthe tops of the inverted T- hars and the pans through which return airentering through slot can pass into the attic. With reference to FIG. 4it will be seen that pan 20 is closed above the slot 100 with a hatshaped retainer 86 spot welded to the top of the pan to receive and holdair plenum duct section 14. As illustrated, the return air passageincludes nested weir 38 and 40 supported between channels 42 and 44 inthe same manner as in the air bar construction-The purpose of the nestedweirs in the return air assembly is merely for aesthetics in that theyblock the direct line of sight through slot 100 into the attic.Accordingly, although an air bar assembly is illustrated, a more simplebaffle arrangement could be utilized at the air return areas. The airbar assembly does have the advantage of affording a measure of dampercontrol for return air.

With this arrangement and as illustrated in FIG. 2, it can be seen thatalternating air supplies and air returns 39 and 51 are provided. It willalso be appreciated that the arrangement of air supply and return can bevaried as desired merely by varying the relative position of the pansand a return area can be completely eliminated by removing the returnair bar assemblies 51, and replacing it with a blank off above slot 100.Thus, this overall combination of air plenum and basic support panconstruction results in extreme versatility with simplicity ofconstruction.

In order to provide for economical shipping of the principal or majorspace occupying element of the overall air plenum-pan combination (theduct board), specific duct board construction is provided andillustrated in FIG. 6. In FIG. 6, duct board 14 has been laid out flatand is shown as including relieved portions 90 in the form of cutV-shaped notches extending the length of the duct board. These relievedareas are actually the lines along which the folds are to be made toresultin the general rectangular shape of the air plenum sections. Itwill be appreciated that the same basic relieved notch construction canbe utilized to provide any desired polygon shape.

With this construction of duct board, the duct board to be assembledinto the plenum sections 12, 14, and 16 can be shipped flat therebyoccupying a minimum amount of shipping space for a given size of ductboard. At the job site, the fold lines provide guides for the contractorwho merely makes the folds along relieved portions 90. When the ductboard is so folded, ends 92 result which are spaced from each othersuchthat they rest on opposite sides of openings 62 overlying portions94 of the pan abutting flanges 50 and 54 on one end and flanges 58 and60 on the other. Barbs 96 can be provided at selected points alongflanges 50, 54, 58, and 60 to hold the duct board in its assembledposition. Also, strips of tape can be provided to further hold theassemblies in the polygon shape, i.e. strips 11 can extend not onlyaround the joints of the duct board but also over the underside of thepan. As is perhaps best illustrated in FIG. 3, sections 92 of the ductboard extend parallel to and overlie portions 94 of pan which extendbetween flanges 50- 58 and 54-60 and sections 92 are held securelybetween the opposed flanges and positioned by barbs 96.

A single air plenum can be utilized with a single pan if desired inwhich case its ends are closed. However, preferably, a plurality of suchair plenum combinations are utilized as is illustrated in FIG. 1.Although only three air plenum sections have been illustrated in FIG. I,it will be appreciated that the air plenum sections can be multiplied toextend the complete length of a given room or the width between thebuilding walls wherein they may then extend over a number of rooms. Theadvantage of this type of an arrangement is that. for example, where theassembled plenum combination extends over a number of rooms, crossedtalk between rooms can be minimized by inserting a dam in the airplenum. This is accomplished by physically cutting through the airplenum sections, for example, l2, l4, l6, and inserting the dam in thecut section and taping the cut for seal purposes. Should the room wallsever be moved, the air delivery system can be modified to accommodatethat move by merely relocating the dam in the same manner as justdescribed, the previous cut, of course, being sealed. It will beappreciated that one main air supply inlet '28 is illustrated in FIG. 1but where the length of the air plenum is increased appreciably, morethan one such supply may be required, and would be required in the eventthat the same continuous length of plenum is extending over andservicing a number of different rooms.

Although the openings 62 are shown as being centered as they would befor an interior installation, they can be moved to accommodate perimeterinstallation or installation adjacent a light fixture.

FIG. 7 illustrates yet another alternative embodiment of this invention.In this embodiment the basic pans 18, 20, and 22 having a constructionidentical to that illustrated and described in connection with eitherFIGS. 3 or 5 have air plenum boxes 98 associated with the upper sidesthereof. These boxes each have a sole air supply opening 99 arid extendover only one of the openings 62 in the pan and there is no opencommunication between adjacent boxes as in adjacent plenum sections 12,14, and 16. This does, however, illustrate the versatility of the basicpan support which has been provided. Again, with this alternativeembodiment, the areas adjacent to the openings 62 and which overlieeither slot 100 or 102 can be utilized to provide return air.

I claim:

'1. In combination in a suspended ceiling including a plurality ofceiling members, a plurality of ceiling support members, and meansdefining an elongated, linear slot in said ceiling, the improvement ofan air delivery arrangement comprising, in combination,

means defining agenerally elongated, linear pan having marginal ends andlongitudinal sides,

means defining an elongated opening in said pan having an extensiongenerally parallel to the longitudinal axis of said pan, the length ofsaid opening being less than the length of said pan and said pan beingotherwise closed,

means defining a generally elongated, linear plenum member having wallportions defining a plenum chamber,

means connecting said linear plenum member to said pan with said plenumchamber having open communication with said opening and with a portionof said wall portions engaged with a portion of said pan,

means for delivering air to said plenum chamber for discharge throughsaid opening,

means at said opening for connection to the means defining said slotalong only a limited length of said slot corresponding generally to thelength of said opening so that air will be discharged through said slotonly through said limited length,

and said pan being spaced from said ceiling support members so that airdelivered to said plenum chamber passes through said opening fordischarge through said slot while the length of said slot adjacent thatthrough which air is discharged underlies a closed extension of said panand provides an air return.

2. The apparatus of claim 1 wherein said means connected at said openingcomprises a diffuser assembly including,

spaced walls projecting laterally relative to said pan and defining apassage therebetween,

and pattern control means in said passage to deflect air flowing throughsaid passage prior to discharge through said slot.

3. The apparatus of claim 1 wherein said means connected at said openingcomprises a collar having spaced side and end walls projecting laterallyrelative to said pan and defining a passage therebetween through whichair from said plenum chamber passes for discharge through said slot.

4. The apparatus of claim 1 wherein said pan includes means forengagement with said linear plenum member to connect said linear plenummember to said pan,

and wherein said opening is spaced inwardly from the longitudinal sidesof said pan.

5. The apparatus of claim 1 wherein said linear plenum member ispolygonal in transverse cross-section and is relieved at the fold linesthereof to accommodate the formation of the corners of said polygonshape,

and said pan including means for engagement with said linear member toconnect said linear plenum member to said pan and hold said linearplenum member in said polygon shape.

6. The apparatus of claim 5 wherein said pan includes flanges along thelongitudinal sides of said pan projecting from the basic plane of saidpan, wherein means is provided along the longitudinal edges of saidopening to provide flanges projecting from said basic plane in the samedirection as said flanges along the longitudinal sides of said pan,

and wherein said linear plenum member wall portions include portionsextending along said pan and engaged between said longitudinal side panflanges and said opening flanges to hold said linear plenum member onsaid pan.

7. The combination of claim 1 wherein said ceiling support memberscomprise a first set of mutually parallel ceiling support members and asecond set of mutually parallel ceiling support members arrangedgenerally perpendicular to said first set,

including a plurality of said pans arranged end-to-end and all generallyidentical in construction and each having a length greater than thespacing between adjacent ones of said first set of ceiling supportmembers,

including a plurality of said linear plenum members connected end-to-endparallel to said second set of ceiling support members,

and wherein at least two of said pans include said opening and saidmeans connected at said opening, one opening and the means connectedthereto spaced from the other opening and the means connected to it,

so that air delivered to said plenum chamber passes through saidopenings for discharge through longi' tudinally spaced portions of saidslot while the lengths of said slot adjacent those longitudinally spacedslot portions through which air is discharged underlie closed extensionsof said pans and provide air returns.

8. The apparatus of claim 7 wherein said means connected at saidopenings comprise diffuser assemblies including spaced walls projectinglaterally relative to said pans and defining a passage therebetween,

and pattern control means in said passage to deflect air flowing throughsaid passage prior to discharge through said slot. 9. The apparatus ofclaim 7 wherein said means connected at said openings each comprise acollar having spaced side and end walls projecting laterally relative tosaid pans to define a passage therebetween through which air from saidplenum chamber passes for discharge through said slot.

10. The apparatus of claim 8 wherein the ceiling support members of saidfirst set are equally spaced, 1

wherein said pans each have a length substantially twice the spacingbetween adjacent ceiling support members of said first set,

and wherein said diffusers have a length substantially equal to thespacing between adjacent ceiling sup port members of said first set.

11. The apparatus of claim 9 wherein the ceiling support members of saidfirst set are equally spaced,

wherein said pans each have a length substantially twice the spacingbetween adjacent ceiling support members of said first set,

and wherein said diffusers have a length substantially equal to thespacing between adjacent ceiling support members of said first set.

12. The apparatus of claim 7 wherein said linear plenum members arepolygonal in transverse cross section and are relieved at the fold linesthereof to accommodate the formation of the comers of said polygonshape,

and said pans include means for engagement with said linear plenummembers to connect said linear plenum members to said pans and hold saidlinear plenum members in said polygon shape.

13. The apparatus of claim 7 wherein said pans include flanges along thelongitudinal sides of said pan projecting from the basic plane of saidpans,

wherein means is provided along the longitudinal edges of each of saidopenings to provide flanges projecting from said basic plane in the samedirection as said longitudinal side pan flanges,

and wherein said linear plenum member wall portions include portionsextending along said pans and engaged between said longitudinal side panflanges and said opening flanges to hold said linear plenum members onsaid pan.

14. The apparatus of claim 1 including a plurality of generally planarextractor blades,

and means connecting said extractor blades in said opening at an angleto said pan and for independent pivotal movement about an axis generallyparallel to said pan.

15. In combination with a generally planar suspended ceiling meansdefining an elongated slot in said ceiling,

first and second generally elongated pans each having a pan surfaceterminating in marginal ends and sides, said first and second pansarranged end-toend and with said pan surface spaced above said meansdefining said slot,

means including wall portions defining a generally elongated air plenumchamber,

' means defining an opening in each of said pans with the opening in oneof said pans being spaced from the opening in the other of said pans,

said pan surfaces being closed except for said openings,

means connecting said plenum chamber to said pans with a part of thewall portions thereof engaged with said pans and with said air plenumchamber having open communication with said openings.

means for delivering air to said air plenum chamber for dischargethrough said openings,

and passage means extending between said openings and the portions ofsaid slots underlying said openings and defining a passage for directingair passing through said openings to and for discharge through saidportions of said slot underlying said openings,

the portions of said slot adjacent the portions of said slots throughwhich air is discharged underlying said closed portions of said pans sothat air may return therethrough into the area above said sus-

1. In combination in a suspended ceiling including a plurality of ceiling members, a plurality of ceiling support members, and means defining an elongated, linear slot in said ceiling, the improvement of an air delivery arrangement comprising, in combination, means defining a generally elongated, linear pan having marginal ends and longitudinal sides, means defining an elongated opening in said pan having an extension generally parallel to the longitudinal axis of said pan, the length of said opening being less than the length of said pan and said pan being otherwise closed, means defining a generally elongated, linear plenum member having wall portions defining a plenum chamber, means connecting said linear plenum member to said pan with said plenum chamber having open communication with said opening and with a portion of said wall portions engaged with a portion of said pan, means for delivering air to said plenum chamber for discharge through said opening, means at said opening for connection to the means defining said slot along only a limited length of said slot corresponding generally to the length of said opening so that air will be discharged through said slot only through said limited length, and said pan being spaced from said ceiling support members so that air delivered to said plenum chamber passes through said opening for discharge through said slot while the length of said slot adjacent that through which air is discharged underlies a closed extension of said pan and provides an air return.
 2. The apparatus of claim 1 wherein said means connected at said opening comprises a diffuser assembly including, spaced walls projecting laterally relative to said pan and defining a passage therebetween, and pattern control means in said passage to deflect air flowing through said passage prior to discharge through said slot.
 3. The apparatus of claim 1 wherein said means connected at said opening comprises a collar having spaced side and end walls projecting laterally relative to said pan and defining a passage therebetween through which air from said plenum chamber passes for discharge through said slot.
 4. The apparatus of claim 1 wherein said pan includes means for engagement with said linear plenum member to connect said linear plenum member to said pan, and wherein said opening is spaced inwardly from the longitudinal sides of said pan.
 5. The apparatus of claim 1 wherein said linear plenum member is polygonal in transverse cross-section and is relieved at the fold lines thereof to accommodate the formation of the corners of said polygon shape, and said pan including means for engagement with said linear member to connect said linear plenum member to said pan and hold said linear plenum member in said polygon shape.
 6. The apparatus of claim 5 wherein said pan includes flanges along the longitudinal sides of said pan projecting from the basic plane of said pan, wherein means is provided along the longitudinal edges of said opening to provide flanges projecting from said basic plane in the same direction as said flanges along the longitudinal sides of said pan, and wherein said linear plenum member wall portions include portions extending along said pan and engaged between said longitudinal side pan flanges and said opening flanges to hold said linear plenum member on said pan.
 7. The combination of claim 1 wherein said ceiling support members comprise a first set of mutually parallel ceiling support members and a second set of mutually parallel ceiling support members arranged generally perpendicular to said first set, including a plurality of said pans arranged end-to-end and all generally identical in construction and each having a length greater than the spacing between adjacent ones of said first set of ceiling support members, including a plurality of said linear plenum members connected end-to-end parallel to said second set of ceiling support members, and wherein at least two of said pans include said opening and said means connected at said opening, one opening and the means connected thereto spaced from the other opening and the means connected to it, so that air delivered to said plenum chamber passes through said openings for discharge through longitudinally spaced portions of said slot while the lengths of said slot adjacent those longitudinally spaced slot portions through which air is discharged underlie closed extensions of said pans and provide air returns.
 8. The apparatus of claim 7 wherein said means connected at said openings comprise diffuser assemblies including spaced walls projecting laterally relative to said pans and defining a passage therebetween, and pattern control means in said passage to deflect air flowing through said passage prior to discharge through said slot.
 9. The apparatus of claim 7 wherein said means connected at said openings each comprise a collar having spaced side and end walls projecting laterally relative to said pans to define a passage therebetween through which air from said plenum chamber passes for discharge through said slot.
 10. The apparatus of claim 8 wherein the ceiling support members of said first set are equally spaced, wherein said pans each have a length substantially twice the spacing between adjacent ceiling support members of said first set, and wherein said diffusers have a length substantially equal to the spacing between adjacent ceiling support members of said first set.
 11. The apparatus of claim 9 wherein the ceiling support members of said first set are equally spaced, wherein said pans each have a length substantially twice the spacing between adjacent ceiling support members of said first set, and wherein said diffusers have a length substantially equal to the spacing between adjacent ceiling support members of said first set.
 12. The apparatus of claim 7 wherein said linear plenum members are polygonal in transverse cross section and are relieved at the fold lines thereof to accommodate the formation of the corners of said polygon shape, and said pans include means for engagement with said linear plenum members to connect said linear plenum members to said pans and hold said linear plenum members in said polygon shape.
 13. The apparatus of claim 7 wherein said pans include flanges along the longitudinal sides of said pan projecting from the basic plane of said pans, wherein means is provided along the longitudinal edges of each of said openings to proVide flanges projecting from said basic plane in the same direction as said longitudinal side pan flanges, and wherein said linear plenum member wall portions include portions extending along said pans and engaged between said longitudinal side pan flanges and said opening flanges to hold said linear plenum members on said pan.
 14. The apparatus of claim 1 including a plurality of generally planar extractor blades, and means connecting said extractor blades in said opening at an angle to said pan and for independent pivotal movement about an axis generally parallel to said pan.
 15. In combination with a generally planar suspended ceiling means defining an elongated slot in said ceiling, first and second generally elongated pans each having a pan surface terminating in marginal ends and sides, said first and second pans arranged end-to-end and with said pan surface spaced above said means defining said slot, means including wall portions defining a generally elongated air plenum chamber, means defining an opening in each of said pans with the opening in one of said pans being spaced from the opening in the other of said pans, said pan surfaces being closed except for said openings, means connecting said plenum chamber to said pans with a part of the wall portions thereof engaged with said pans and with said air plenum chamber having open communication with said openings, means for delivering air to said air plenum chamber for discharge through said openings, and passage means extending between said openings and the portions of said slots underlying said openings and defining a passage for directing air passing through said openings to and for discharge through said portions of said slot underlying said openings, the portions of said slot adjacent the portions of said slots through which air is discharged underlying said closed portions of said pans so that air may return therethrough into the area above said suspended ceiling. 